A color filter used for a liquid crystal display is a member which allows only the light of a necessary wavelength region to transmit the color filter from white light of the back light passing through the color filter by disposing a plurality of colors regularly on a transparent glass substrate to realize a color display of the display. The color used for the color filter generally includes three primary colors such as red, green, and blue, and for adjusting each transmission spectrum, improvement of a color material, a resin used an additive, or the like, which is used, has been conducted repeatedly. Among these, from a viewpoint of enhancing display quality, an increase in luminance and expansion of a color reproducibility range have been demanded to a green coloring agent for color filters.
In order to increase luminance, it is important to select a pigment having high transmittance with respect to back light, and the luminance has been improved by using the pigment green 58 as a major pigment instead of the conventional pigment green 36. Also, as the luminance has been increased due to the improvement of the pigment, white light of the back light can be used effectively and accordingly, energy or the manufacturing cost of the display can be decreased.
For the expansion of the color reproducibility range, it is necessary to increase chroma of the color material included in a color filter. In order to produce a coating film with high chroma, a method for increasing a pigment concentration in the coating film or a method of increasing the thickness of the coating film with the same pigment concentration is exemplified. However, it is difficult to secure every resistance of the coating film in any cases, and accordingly the pigment green 7 has been selected as a major pigment, which enables a decrease in the film thickness in a specific chromaticity after mixing with a yellow color material, rather than the pigment green 36 or the pigment green 58 which has been used for the conventional color filter. An expansion of the color reproducibility range can be possible due to the increase in film thickness using the pigment, green 36 or the pigment green 58, but it is not possible to achieve 90% or more of the NTSC ratio with a practical film thickness, which is the reason why the pigment green 7 is selected. For example, it is suggested to form a green pixel using a green photosensitive resin composition containing the pigment green 7 and the pigment yellow 185 to achieve high color reproducibility with a thin film having a thickness of 2.2 μm or less. However, since the pigment green 7 has low transmittance compared to the pigment green 36 and the pigment green 58, there is a problem in that luminance of the obtained display is decreased. Furthermore, an increase of the light intensity of the back light may compensate for luminance, but a new problem occurs such as an increase in electric power consumption and accordingly an improvement is demanded. As described above, a color material for color filters satisfying both luminance and color reproducibility is demanded.
In order to solve this problem, it is suggested to use a dye compound as a color material for color filters in order to increase luminance. The dye compound often is a dye having fluorescent light and it is suggested to provide a color filter having high luminance and a high contrast ratio by suppressing fluorescence of the dye having fluorescent light. In order to suppress the fluorescence and improve dispersibility, an addition of a pigment derivative having a substituent introduced into various pigment skeletons has been suggested (PTL 1).
Similarly, as a coloring composition for color filters having an excellent contrast ratio of color filters, dispersion stability, and chemical resistance, a coloring composition for color filters including a phthalocyanine pigment having a pigment and a substituent has been suggested (PTL 2).
Also, for a color filter having high color reproducibility, the use of a pigment such as the pigment green 7 and the pigment green 58 has been suggested, but sufficient luminance is not obtained and there is a problem in that the thickness of a color filter becomes large in the production of the film (PTL 3).
In order to form a color filter having increased luminance and expanded color reproducibility range, these conventional technologies are insufficient and the objective has not been achieved yet.